1. Technical Field
The present application relates generally to an improved apparatus for moving electronics in at least two degrees of freedom. More specifically, the present application is directed to an apparatus having a single coil pair, multiple axis inductive power coupling which eliminates the need to use brushes or the like to provide an electrical contact for providing electrical power to electronics coupled to the apparatus.
2. Description of Related Art
In a number of different types of apparatus, electronics must be able to be moved in a rotating manner through one or more degrees of freedom. Typically, the electrical power for running the electronics must be provided to the electronics via electrical lines provided on the support structure for the electronics. The support structure must be configured to permit the rotation motion of the electronics. Thus, in order to provide the electrical power along lines of a rotational support structure, electrical contact brushes or inductive power coupling coil pairs are used to provide an electrical contact with a power source.
Electrical brushes and brush materials are used in conjunction with slip rings, commutators, or other contact surfaces to maintain an electrical connection in rotary and linear sliding contact applications. Electrical brushes and brush materials require very good frictional characteristics combined with high to moderate conductivity. Electrical brushes may be made from a plurality of different types of materials depending on the particular use for which they are intended. For example, graphite brush materials are used for high power equipment while metal brushes or sliding contacts are used for signal or low power applications.
Inductive power coupling coil pairs comprise two coils of electrical conductors, i.e. wire, one coil acting as a primary transformer coil and the other coil acting as the secondary transformer coil. An electrical current is passed through the primary transformer coil which causes a magnetic flux due to the windings of the primary transformer coil. The magnetic flux inductively imparts an electrical current in the secondary transformer coil. Because the electrical current is created in the secondary transformer coil through induction, it is not necessary that the two coils be physically attached to transfer the electrical current. Thus, a greater degree of freedom of motion is achievable through use of the inductive power coupling coil pair.
FIG. 1 is an exemplary diagram of a known rotary electronics support structure in which electrical contact brushes are utilized. As shown in FIG. 1, the support structure comprises a first arm A 120 that rotates about a first axis, i.e. the Y-axis, and a second arm B 110 that rotates about a second axis, i.e. the X-axis. The arms are coupled to coils of an inductive power coil pair comprising an inner coil 140 and an outer coil 150. The inner coil 140 and the outer coil 150 are concentric and aligned or oriented such that they are both in the same plane, i.e. the X-plane in the depicted example.
The outer coil 150, which operates as the secondary transformer coil, rotates with arm A 120, i.e. is fixed to arm A 120, and provides power to electronics (not shown) which may be attached to the end of arm A 120 via one or more wires running along the arm A 120 from the outer coil 150. The inner coil 140 operates as the primary transformer coil of the inductive power coupling coil pair and thus inductively couples power into the outer coil 150. The inner coil 140 is attached or fixed to the arm B 110. Thus, by rotating arm B 110 about the X-axis, the entire support structure is rotated around the X-axis. Meanwhile, arm A 120 is rotatable around the Y-axis at the same time.
Since arm B 110 rotates about the X-axis, electrical contact brushes 130, or an additional inductive power coupling coil is required to connect a power source to the entire apparatus. That is, the electrical contact brushes 130, or an additional inductive power coupling coil, provides a contact with a power source (not shown) and is coupled to wires providing a current to the inner coil 140. The inner coil 140 inductively couples power into the outer coil 150 due to the current and a motion of the arm A 120 about the Y-axis which causes a magnetic flux on the outer coil 150. The power in the outer coil 150 is then provided to the electronics (not shown) attached to arm A 120 via one or more wires attached to arm A 120.
Electrical contact brushes have several disadvantages. Electrical contact brushes wear out over time due to the friction between the electrical contact brush and their corresponding contact. Electrical contact brushes are mechanical in nature and thus, are susceptible to mechanical wear and failure. Moreover, electrical contact brushes cause a great deal of electromagnetic interference/radiation and thus, are electrically noisy. Finally, electrical contact brushes have substantial electrical resistance/impedance.
While it is true that, instead of an electrical contact brush as shown in FIG. 1, one can couple energy through an additional inductive power coupling coil, such as the coils 140 and 150, such inductive power coupling coils have a great deal of energy loss, i.e. the amount of power transferred is limited. Therefore, a second inductive power coupling coil pair (to replace the depicted electrical contact brushes 130 in FIG. 1, for example) would result in insufficient power coupling.